This invention is concerned with apparatus for handling electrical or electronic components, for example in a component placement machine. The components may be of a variety of shapes and sizes, for example so-called flat packs, S.0. style transistors, leadless chip carriers, dual in line packages, melf-type components and the like, as well as so-called "chips".
In the manufacture of electrical or electronic apparatus it is necessary to assemble a plurality of components on a suitable substrate, for example a printed circuit board. A number of systems have been proposed for handling the components to be placed on a substrate and many of these have proposed the use of pick-up heads having a suitable tool by which a component may be picked up. The tools have been of various types, depending on the components to be handled to some extent; for example the tools may mechanically grip the components or may use suction or a magnetic system to retain a component on the tool of the pick-up head when the component is removed from a suitable component supply means for delivery elsewhere for example to a suitable placement position where the component may be placed on a substrate e.g. a printed circuit board. It is important to ensure that the components are correctly oriented when placed on a printed circuit board and one such means for orienting a component is described in our PCT Patent Application Publication No. WO 85/03404. In patent application components are retained on the pick-up head using suction, the components being centered and oriented relative to an axis of the head by means of jaws which engage the component to center it. Orientation of the component is then achieved by rotating the head about its axis. In British patent No. 2096498 is described a mechanism for mounting chip type circuit elements comprising an indexing member and a plurality of mounting heads mounted on said indexing member, each mounting head including a mounting head shaft mounted for both rotation and for axial sliding movement, a suction pin mounted on an end of the mounting head shaft and adapted to pick up and hold a circuit element, and gear means for transmitting rotational torque to the mounting head shaft. In the machine described by way of example in this British patent the gear means on a mounting head is engaged by a gear when the head is carried by an indexing member to a position at which the gear is disposed for rotating the mounting head to an appropriate position. In the mechanism described a pulse motor (otherwise known as a stepping motor) rotates the gear so that the mounting head is rotated through 15.degree. for each operating step of the pulse motor 72. A lock mechanism is provided by which the mounting head is locked in a particular position unless it is necessary to alter the mounting direction of the circuit element. The locking mechanism includes a lock lever the front end of which engages the gear means provided on the mounting head to prevent rotation thereof. Whilst the mechanism described in this British patent may be effective to provide a coarse orientation of the circuit element it is inappropriate for a very precise orientation of a circuit element which is necessary in the most accurate machines. The system described in the British patent requires gears to be provided on each head which, to achieve satisfactory precision, must have a very fine pitch and be precisely machined--the provision of such gears is expensive. Moreover, the system of engaging the gear means on the mounting head with a static gear at an appropriate position during rotation of the indexing member requires that the static gear mesh with the gear means on the mounting head--problems are likely to arise in achieving meshing of the static gear and the gear means on the mounting head without damage to the gears. Furthermore, a system of locking the mounting head against rotation which relies upon the mechanical engagement of a locking member between the teeth of the gear means on the mounting head is also likely to lead to damage of the gear and militates against rotational accuracy better than the angle between adjacent gear teeth. In addition the use of a gear train as described may lead to considerable inertia in operation of the gear means and provides a somewhat bulky mounting head. A further disadvantage of the mechanism described in the aforementioned British patent is the use of a pulse motor to effect rotation--this places a restriction on both rotational accuracy (unless complex gear trains are used) and provides limitations on the speed of operation due to the rate at which pulse motors can be accelerated and decelerated during their operation.
One of the various objects of the present invention is to provide apparatus for handling electrical or electronic components comprising a pick-up head having improved means by which components carried by the pick-up head may be rotated to a desired orientation.